Linear amplifier 4cx5000a

JOHN 5-19 LAMIA *HIGH POWER AMPLIFIER 4CX5000A*

An AM Transmitter Modification and Construction Project.

............. 4CX5000A SINGLE TUBE GROUNDED SCREEN!!!

My Linear is a class AB1 high frequency amplifier utilizing the Eimac 4CX5000A power tetrode. It is operating on the 176m. A 4CX5000a will work in the circuit with little modifications. -->The Screen of the tube is physically connected to the ground.

The 'grounded screen' may be a bit confusing to those of us used to using tetrodes in the more conventional manner, with the cathode at chassis potential. Due to the design of this cavity, the screen is indeed at "ground" for RF; for DC, it can be more precisely described as being connected directly to the chassis. This requires a bit more complexity in the design of the power supply.

The grounded screen configuration results in better isolation of plate from grid circuits; therefore, better over-all stability!!!! Power output over 10kw could then be expected. Power was measured with a Bird 43 wattmeter and a 10 KW slug (Frequency Band 0.45-2.5 mhz)
HOME MADE LINEAR AMPLIFIER 4CX5000A

...................... 1690 KHZ AM

This is a 4CX5000a grid driven amplifier that is built like a tank. The unit is considerably over designed as can be seen in the pictures documenting the construction. The unit requires a separate screen power supply and High Voltage power supply. The documentation indicates a well thought out design and construction technique.

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Below you can find some pictures of my "Shack".

Click on the photo description for a larger picture.

Output Power
In order to achieve full power output over 10000 watts continuous carrier, an input power approximately 10 to 40 watts is required. If your delivers more output power, reduce the drive level.
For the amplifier RF output, I used an LC type connectors at the time of construction. The LC type seems to handle the power levels without any problems (so far!).

Tube Protection
The linear has a very sophisticated tube protection circuitry, designed to protect excessive plate current, screen grid current, screen grid voltage, bias voltage, overdrive, SWR. The tube is also protected from excessive temperature by continuously monitoring the required airflow temperature. In case of any fault, the amplifier is automatically cut off. A resistor in the B+ circuit and a MOV in the screen circuit further protects the tube and the power supply from a possible tube internal flash-over.

In the center of the photo is a shaped parasitic choke with two, 3 watt, 100 ohm carbon resistors across it.

TubeThe linear operates with one 4cx5000a/8170 tube, in Class AB1 with a plate dissipation of 6000 watts.Constructed primarily for military communication, this tube is physically and electrically exceptional rugged and with additional sophisticated protection circuitry incorporated, the linear is almost indestructible. The 4cx5000a/8170 tube is a compact high slope and when operated under normal conditions, will last a very long time. Class AB1 amplifiers are roughly 60% efficient. The zero-signal anode-current in a Class AB1 amplifier is normally set to about 20% of the maximum-signal single-tone anode-current. In a typical HF amplifier, the drive power required for Class AB1 operation is roughly 1% to 2% of the output power. Most of the tubes that are used in Class AB1 RF amplifier service are tetrodes and pentodes--devices that have the advantage of grid-to-screen amplification.

Cooling
A lot of attention was given to the design of the linear cooling system. A pressurized forced air cooling to achieve with a rugged temperature controlled 850 CFM blower (turbine) which effectively cools all critical components of the amplifier. The volume of cooling air far exceeds manufacturers' specifications for all critical components. The blower is positioned in such a way that it prevents hot air being circulated through the system.

Eimac SK-300A and Y-309 Bypassed socket for the 4CX5000A/10000D/15000A... series tubes.

Front view of completed tank with air chimney in place.

The picture above shows the typical Pi tank circuit configuration.

The plate tank circuit is a pi-network that matches the high impedance of the plate to the low impedance of the antenna. At the same time the circuit filters out undesired harmonics from the output signal. The signal from the plate enters through the .001 uf plate coupling capacitor. The 1000 pf 12,5kv plate tuning capacitor tunes the plate to resonance and the 2000 pf load capacitor (actually an assembly of switched fixed capacitors) adjusts the network for the best impedance match. If the plate tuning cap does not have enough capacitance the same method can be use to add capacitance.The tank coil consists of 45µH, a rolling inductor no need RF power switch.

can be seen in the photo.

Tuning:

Keep eyes on the screen current while tuning the PA. The screen current will go drastically negative (-10mA) if the cavity is tuned too low in frequency.

-->The Screen current must be + 1 to -1mA when tuned correctly. Adjust input and output tuners for maximum power.

The blocking capacitors used were two pair of 1000pF attached to a copper strap that is copper soldered to the anode clamp. The coil side of the connection is to a copper plated brass plate, with the coil silver soldered to it.

An RF choke of 2.5mH is grounded to the chassis from the output terminal. This choke is for safety, should plate DC voltage ever appear on the tank circuit, the choke will short it to ground and cause the (HI VOLTAGE POWER SUPPLY) to trip off-line. The choke also shunts to ground any static buildup on the antenna, and shorts it to ground when the amp is keyed into transmit.

High-Voltage Power Supply.

High-Power RF Amplifiers High-Voltage, High-Current Power Supplies ….

One of the main items that is needed for a good amp is a good power supply.

These voltages can kill you...
keep your hands OUT!

HF BANDS QRP HI POWER LINEAR AMPLIFIER .An AM Transmitter Modification and Construction Project. -->

1.6 - 30MHz (All Ham bands)

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Line Section, 1-5/8" EIA Flange Single Element Socket - 4712-000

-->AM PLL TRANSMITTER EXCITER 522-1800KHZ -->PLL Synthesizer Variable Power Output,swr Protection. The Best For Radio Station!!

My Ham Radio Gear

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The Classic Collins R-388A/URR (51j-4)HF communications receiver with Motorola andElectronic Assistance Corporation R-390A/URR. The 51J-4 is the predecessor to the R-390/URR and the improved R-390A/URR.

The R-390A/URR, a military communications receiver built from 1955 to 1984, is still regarded as one of the best HF receivers around. Covering .5 to 32MHz in 32 bands and equipped with 26 vacuum tubes. Designed by Collins in 1955 as a low-cost replacement to it's predecessor, the R-390/URR, the R-390A/URR uses 26 tubes instead of it's predecessor's 32, and mechanical filters in place of crystal ones. My receivers R-390A was built not by Collins, but Motorola 1956 0014-PH-56 and Electronic Assistance Corporation ( 1967 DAABO5-67-C-0155 ). Over 55,000 R-390A receivers were manufactured by Collins, Motorola, Imperial, EAC, Teledyne, Stewart-Warner, Capehart, etc. from about 1954 to 1984.
The 455 kHz IF utilizes crystal filters for 0.1 and 1 kHz bandwidths and mechanical filters for 2, 4, 8 and 16 kHz bandwidths. Operational capability of the receiver allows for remote control of the AGC and RF gain adjustments.
My R-390A is fairly complete, is in prety good shape, and works quite well.
The R390A/URR is without question the best receiver (in my opinion) mass produced.

Here are pictures of my Collins R-388/URR receiver.Collins Radio Company manufactured a lot of 51J3 and 51J4 receivers in the beginning of 1950's for the US Armed Forces, where they were called as R-388/URR and R-388A/URR.

This particular model receiver has a special place in my heart !!!!

I know Collins is a very respectable name in ham radio.
Data plate of my Collins R-388/URR

and here you can see the s-meter of this receiver.
The meter is calibrated in 20-,40-,60-,80-,and 100-db input signal levels and -10 to +6 db audio output level.

This is the military version of the Collins 51J-3 communication receiver, Covering .5 to 30MHz, the R-388 has linear tuning over the entire frequency span. It is very stable and accurate utilizing the Collins 70E PTO. It features a built-in 100kc crystal calibration oscillator that can be compared directly against WWV.Checking dial calibration every 1/10-mc interrval throughout the tuning range .

The R- 388/urr has a standard crystal filtering system. Only the 51J-4 version is equipped with the famous mechanical Collins IF filters, I consider the 3 and 6 kHz filters as very useful for AM reception, in some situations they are even better suited then the filters found in the R-390A.The receiver power supply can be operated from a 115 volt, 45 to 70 hz source and has provisions for 230 volt operation.

............................................................ 51J-4

Collins R-392/URR Mobile Communications US Army Receiver.

Looking for some more photo of my R-392/URR military receiver.

The R392 is a communications receiver used by the US Army after 1954.

Range 0.5 to 32 MHz in 32 bands, AM/CW/MCW with BFO.

TM 11-858.pdf Instruction Book for Radio Receiver R-392/URR. 29 June 1954.

This unit was manufactured by Stewart Warner. A number of these units were manufactured by Collins.

Receiver: R-392/URR provides continuous tuning and calibration every 100 kHz throughout its range.

The receiver was designed with a watertight (!)

The receiver was typically mounted on a Jeep!!!

Icom IC -R8500 - Wideband Communications Receiver.
-->The Icom IC-R8500 Communications Receiver is probably the only receiver you will ever need, with superb coverage from 0.1- 2000Mhz in all modes SSB (USB, LSB), CW, AM, FM and WFM are included.

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The R8500 has both a Noise Blanker circuit and Intermediate Frequency Shift that really help reduce or eliminate interference on shortwave frequencies.
The ICOM's Audio Peak Filter is also very effective at helping voices to 'pop out' of the HF background noise."

The IC-R8500 cosmetically is a very attractive receiver

The IC-R8500 is a high specification communications receiver ideal for the radio amateur.This handsome receiver is a terrific centerpiece or complement to any listening shack

More photo of SIEMENS E-311 receiver.E-311 Shortwave Receiver 1,5 - 30 mhz

The E 311 is probably one of the best tube receivers for FSK and SSB ever built.

This receiver was designed in 1959 for AM, CW, FSK and SSB reception. It was widely used by different government authorities and in military applications. It could be found on board of most German ships in the Sixties and Seventies. As a tube receiver the E 311 has an incredible setting accuracy of 100 Hz and an impressive stability of 20 Hz over 24 hours. The tuning scale has an effective length of 285 m. Excellent for AM reception in an ECSS mode as well.

-->Here's another favorite receiver.

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More photo of my BC-312N & (M) military receiver.

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The BC-312 is a World War II military radio receiver with HF band coverage 1.5-18.1 MHz, six bands, AM/CW, Crystal filter, 915 KHz, BFO, MVC/AVC. It was used primarily as part of field installations and mobile communication vehicles.

Here are two BC-312 receivers model "N"& model "M". These work surprisingly well for AM and CW, and can also receive SSB with careful BFO tuning

MFJ-259B SWR antenna analyzer MODIFICATION 1.5-170 MHZ BY JOHN 5-19

AM Radio Transmission at Night

Radio signals are electromagnetic waves that are sent from a transmitter to one or more receivers. All electromagnetic waves travel at the speed of light, but they can have different wavelengths and frequencies. First of all, there is the AM band of frequencies. These are electromagnetic waves with frequencies between 535 kHz and 1605 kHz with an extension to 1710 kHz in the US.
In most of the US, mediumwave stations are separated by 10 kHz and have two sidebands of ±5 kHz. In the rest of the world, the separation is 9 kHz, with sidebands of ±4.5 kHz.

AM station's signal travels depends on such things as the station's frequency, the power of the transmitter in watts, the nature of the transmitting antenna, how conductive the soil is around the antenna [damp soil is good; sand and rocks aren't], and, a thing called ionospheric refraction. The ionosphere is a layer of heavily charged ion molecules above the earth's atmosphere. It extends over altitudes from about 50 km to about 600 km. It is used by radio operators as a surface from which signals can be reflected to distant stations. AM signals can be reflected from the ionospheric layer back to earth, so that the signals can reach unintended places that are thousands of miles away. Further, the ionospheric reflection is increased during the night time. Note that for AM radio stations the ground wave doesn't go very far.

During the day, AM signals travel by groundwave, diffracting around the curve of the earth over a distance up to a few hundred kilometers from the signal transmitter. However, after sunset, changes in the ionosphere cause AM signals to travel by skywave, enabling AM radio stations to be heard much farther from their point of origin than is normal during the day.THE IONOSPHERIC WALL
Because of the solar ionization and also other smaller ionization effects as meteors, or even high energetic radiation from the space infinity, the ionosphere becomes a conducting wall that can reflect the waves, as light is reflected on a mirror.

One of the more important performance characteristics of an antenna system is its angle of radiation.

The higher the antenna above ground, the lower the radiation angle.

This is the angle at which the signal leaves the antenna . The signal is fired in all directions and at all angles, but there's a concentration in certain directions and at certain angles. This concentration, or lobe, depends on many factors. One of the main factors is the antenna's height above the ground. The higher the antenna, the lower the radiation angle. This is great for DX as the signal travels at a low angle for many kilometers before glancing off the ionosphere and returning at a low angle to the Earth.

------- H.A.A.R.P ----------(High-frequency Active Aural Research Programme)

Η ΚΑΤΑΣΡΟΦΗ ΤΗΣ ΙΟΝΟΣΦΑΙΡΑΣ

Το HAARP αποτελεί στην ουσία μια εξελιγμένη μορφή «ιονοσφαιρικού θερμαστή»...........κ.λ.π

More to follow..........Μην ανησυχείτε για το τι σκέφτονται οι άλλοι για σας γιατί απλώς οι άλλοι δεν σας σκέφτονται. Αναρωτιούνται μόνο τι σκέφτεστε εσείς για αυτούς.